Kbuild: Use dtc's -d (dependency) option

This hooks dtc into Kbuild's dependency system.

Thus, for example, "make dtbs" will rebuild tegra-harmony.dtb if only
tegra20.dtsi has changed yet tegra-harmony.dts has not. The previous
lack of this feature recently caused me to have very confusing "git
bisect" results.

For ARM, it's obvious what to add to $(targets). I'm not familiar enough
with other architectures to know what to add there. Powerpc appears to
already add various .dtb files into $(targets), but the other archs may
need something added to $(targets) to work.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
[mmarek: Dropped arch/c6x part to avoid merging commits from the middle
of the merge window]
Signed-off-by: Michal Marek <mmarek@suse.cz>

5 files changed, 10 insertions, 8 deletions

diff --git a/arch/arm/boot/Makefile b/arch/arm/boot/Makefile
index a1edfd5a129a..816e91bce2f9 100644
--- a/arch/arm/boot/Makefile
+++ b/arch/arm/boot/Makefile
@@ -59,9 +59,11 @@ $(obj)/zImage:	$(obj)/compressed/vmlinux FORCE
 
 endif
 
+targets += $(dtb-y)
+
 # Rule to build device tree blobs
-$(obj)/%.dtb: $(src)/dts/%.dts
-        $(call cmd,dtc)
+$(obj)/%.dtb: $(src)/dts/%.dts FORCE
+        $(call if_changed_dep,dtc)
 
 $(obj)/dtbs: $(addprefix $(obj)/, $(dtb-y))
 
diff --git a/arch/microblaze/boot/Makefile b/arch/microblaze/boot/Makefile
index 4c4e58ef0cb6..0c796cf81586 100644
--- a/arch/microblaze/boot/Makefile
+++ b/arch/microblaze/boot/Makefile
@@ -53,6 +53,6 @@ $(obj)/simpleImage.%: vmlinux FORCE
 DTC_FLAGS := -p 1024
 
 $(obj)/%.dtb: $(src)/dts/%.dts FORCE
-        $(call cmd,dtc)
+        $(call if_changed_dep,dtc)
 
 clean-files += *.dtb simpleImage.*.unstrip linux.bin.ub
diff --git a/arch/openrisc/boot/Makefile b/arch/openrisc/boot/Makefile
index 98ca185097a5..09958358601a 100644
--- a/arch/openrisc/boot/Makefile
+++ b/arch/openrisc/boot/Makefile
@@ -11,5 +11,5 @@ clean-files := *.dtb.S
 
 #DTC_FLAGS ?= -p 1024
 
-$(obj)/%.dtb: $(src)/dts/%.dts
-        $(call cmd,dtc)
+$(obj)/%.dtb: $(src)/dts/%.dts FORCE
+        $(call if_changed_dep,dtc)
diff --git a/arch/powerpc/boot/Makefile b/arch/powerpc/boot/Makefile
index c26200b40a47..5e1f0d5b9eae 100644
--- a/arch/powerpc/boot/Makefile
+++ b/arch/powerpc/boot/Makefile
@@ -334,8 +334,8 @@ $(obj)/treeImage.%: vmlinux $(obj)/%.dtb $(wrapperbits)
         $(call if_changed,wrap,treeboot-$*,,$(obj)/$*.dtb)
 
 # Rule to build device tree blobs
-$(obj)/%.dtb: $(src)/dts/%.dts
-        $(call cmd,dtc)
+$(obj)/%.dtb: $(src)/dts/%.dts FORCE
+        $(call if_changed_dep,dtc)
 
 # If there isn't a platform selected then just strip the vmlinux.
 ifeq (,$(image-y))
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 2ce2e2194f26..00c368c6e996 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -264,7 +264,7 @@ $(obj)/%.dtb.S: $(obj)/%.dtb
         $(call cmd,dt_S_dtb)
 
 quiet_cmd_dtc = DTC     $@
-cmd_dtc = $(objtree)/scripts/dtc/dtc -O dtb -o $@ -b 0 $(DTC_FLAGS) $<
+cmd_dtc = $(objtree)/scripts/dtc/dtc -O dtb -o $@ -b 0 $(DTC_FLAGS) -d $(depfile) $<
 
 # Bzip2
 # ---------------------------------------------------------------------------